An equianalgesic chart is a conversion chart that lists equivalent doses of

analgesic An analgesic drug, also called simply an analgesic, antalgic, pain reliever, or painkiller, is any member of the group of drugs used for pain management. Analgesics are conceptually distinct from anesthetics, which temporarily reduce, and in s ...

s (drugs used to relieve pain). Equianalgesic charts are used for calculation of an equivalent dose (a dose which would offer an equal amount of

analgesia Pain management is an aspect of medicine and health care involving relief of pain (pain relief, analgesia, pain control) in various dimensions, from acute and simple to chronic and challenging. Most physicians and other health professionals ...

) between different analgesics. Tables of this general type are also available for

NSAID Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...

benzodiazepine Benzodiazepines (BZD, BDZ, BZs), colloquially known as "benzos", are a class of central nervous system (CNS) depressant, depressant drugs whose core chemical structure is the fusion of a benzene ring and a diazepine ring. They are prescribed t ...

depressant Depressants, also known as central nervous system depressants, or colloquially known as "downers", are drugs that lower neurotransmission levels, decrease the electrical activity of brain cells, or reduce arousal or stimulation in various ...

stimulant Stimulants (also known as central nervous system stimulants, or psychostimulants, or colloquially as uppers) are a class of drugs that increase alertness. They are used for various purposes, such as enhancing attention, motivation, cognition, ...

anticholinergic Anticholinergics (anticholinergic agents) are substances that block the action of the acetylcholine (ACh) neurotransmitter at synapses in the central nervous system, central and peripheral nervous system. These agents inhibit the parasympatheti ...

s and others.

Format

Equianalgesic tables are available in different formats, such as pocket-sized cards for ease of reference. A frequently-seen format has the drug names in the left column, the route of administration in the center columns and any notes in the right column.

Purpose

There are several reasons for switching a patient to a different pain medication. These include practical considerations such as lower cost or unavailability of a drug at the patient's preferred pharmacy, or medical reasons such as lack of effectiveness of the current drug or to minimize adverse effects. Some patients request to be switched to a different narcotic due to stigma associated with a particular drug (e.g. a patient refusing

methadone Methadone, sold under the brand names Dolophine and Methadose among others, is a synthetic opioid used medically to treat chronic pain and opioid use disorder. Prescribed for daily use, the medicine relieves cravings and opioid withdrawal sym ...

due to its association with

opioid Opioids are a class of Drug, drugs that derive from, or mimic, natural substances found in the Papaver somniferum, opium poppy plant. Opioids work on opioid receptors in the brain and other organs to produce a variety of morphine-like effects, ...

addiction treatment Drug rehabilitation is the process of medical or psychotherapeutic treatment for dependency on psychoactive substances such as alcohol, prescription drugs, and street drugs such as cannabis, cocaine, heroin, and amphetamines. The general inten ...

). Equianalgesic charts are also used when calculating an equivalent dosage of the same drug, but with a different

route of administration In pharmacology and toxicology, a route of administration is the way by which a medication, drug, fluid, poison, or other substance is taken into the body. Routes of administration are generally classified by the location at which the substance ...

Precautions

An equianalgesic chart can be a useful tool, but the user must take care to correct for all relevant variables such as route of administration, cross tolerance,

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

and the

bioavailability In pharmacology, bioavailability is a subcategory of absorption and is the fraction (%) of an administered drug that reaches the systemic circulation. By definition, when a medication is administered intravenously, its bioavailability is 100%. H ...

of a drug. For example, the narcotic

levorphanol Levorphanol (brand name Levo-Dromoran) is an opioid medication used to treat moderate to severe pain. It is the levorotatory enantiomer of the compound racemorphan. Its dextrorotatory counterpart is dextrorphan. It was first described in Ge ...

is 4–8 times stronger than

morphine Morphine, formerly also called morphia, is an opiate that is found naturally in opium, a dark brown resin produced by drying the latex of opium poppies (''Papaver somniferum''). It is mainly used as an analgesic (pain medication). There are ...

, but also has a much longer half-life. Simply switching the patient from 40 mg of morphine to 10 mg of levorphanol would be dangerous due to dose accumulation, and hence frequency of administration should also be taken into account. There are other concerns about equianalgesic charts. Many charts derive their data from studies conducted on opioid-naive patients. Patients with chronic (rather than acute) pain may respond to analgesia differently. Repeated administration of a medication is also different from single dosing, as many drugs have active metabolites that can build up in the body. Patient variables such as sex, age, and organ function may also influence the effect of the drug on the system. These variables are rarely included in equianalgesic charts.

Opioid equivalency table

Opioid Opioids are a class of Drug, drugs that derive from, or mimic, natural substances found in the Papaver somniferum, opium poppy plant. Opioids work on opioid receptors in the brain and other organs to produce a variety of morphine-like effects, ...

s are a class of compounds that elicit

(pain killing) effects in humans and animals by binding to the

μ-opioid receptor The μ-opioid receptors (MOR) are a class of opioid receptors with a high affinity for enkephalins and beta-endorphin, but a low affinity for dynorphins. They are also referred to as μ(''mu'')-opioid peptide (MOP) receptors. The prototypical ...

within the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain, spinal cord and retina. The CNS is so named because the brain integrates the received information and coordinates and influences the activity o ...

. The following table lists opioid and non-opioid analgesic drugs and their relative potencies. Values for the potencies represent opioids taken orally unless another

is provided. As such, their bioavailabilities differ, and they may be more potent when taken

intravenously Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...

Nonlinearities

This chart measures pain relief versus mass of medication. Not all medications have a fixed relationship on this scale.

Methadone Methadone, sold under the brand names Dolophine and Methadose among others, is a synthetic opioid used medically to treat chronic pain and opioid use disorder. Prescribed for daily use, the medicine relieves cravings and opioid withdrawal sym ...

is different from most opioids because its potency can vary depending on how long it is taken. Acute use (1–3 days) yields a potency about 1.5× stronger than that of

and chronic use (7 days+) yields a potency about 2.5 to 5× that of morphine. Similarly, the effect of

tramadol Tramadol, sold under the brand name Tramal among others, is an opioid analgesic, pain medication and a serotonin–norepinephrine reuptake inhibitor (SNRI) used to treat moderately severe pain. When taken by mouth in an immediate-release form ...

increases after consecutive dosing due to the accumulation of its active metabolite and an increase of the oral bioavailability in chronic use.

References